/* Language-level data type conversion for GNU C. Copyright (C) 1987-2022 Free Software Foundation, Inc. This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see . */ /* This file contains the functions for converting C expressions to different data types. The only entry point is `convert'. Every language front end must have a `convert' function but what kind of conversions it does will depend on the language. */ #include "config.h" #include "system.h" #include "coretypes.h" #include "target.h" #include "c-tree.h" #include "convert.h" #include "langhooks.h" #include "ubsan.h" #include "stringpool.h" #include "attribs.h" #include "asan.h" /* Change of width--truncation and extension of integers or reals-- is represented with NOP_EXPR. Proper functioning of many things assumes that no other conversions can be NOP_EXPRs. Conversion between integer and pointer is represented with CONVERT_EXPR. Converting integer to real uses FLOAT_EXPR and real to integer uses FIX_TRUNC_EXPR. Here is a list of all the functions that assume that widening and narrowing is always done with a NOP_EXPR: In convert.cc, convert_to_integer. In c-typeck.cc, build_binary_op (boolean ops), and c_common_truthvalue_conversion. In expr.cc: expand_expr, for operands of a MULT_EXPR. In fold-const.cc: fold. In tree.cc: get_narrower and get_unwidened. */ /* Subroutines of `convert'. */ /* Create an expression whose value is that of EXPR, converted to type TYPE. The TREE_TYPE of the value is always TYPE. This function implements all reasonable conversions; callers should filter out those that are not permitted by the language being compiled. INIT_CONST is true if the conversion is for arithmetic types for a static initializer and folding must apply accordingly (discarding floating-point exceptions and assuming the default rounding mode is in effect). */ static tree c_convert (tree type, tree expr, bool init_const) { tree e = expr; enum tree_code code = TREE_CODE (type); const char *invalid_conv_diag; tree ret; location_t loc = EXPR_LOCATION (expr); if (type == error_mark_node || error_operand_p (expr)) return error_mark_node; if ((invalid_conv_diag = targetm.invalid_conversion (TREE_TYPE (expr), type))) { error (invalid_conv_diag); return error_mark_node; } if (type == TREE_TYPE (expr)) return expr; ret = targetm.convert_to_type (type, expr); if (ret) return ret; STRIP_TYPE_NOPS (e); if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (TREE_TYPE (expr)) && (TREE_CODE (TREE_TYPE (expr)) != COMPLEX_TYPE || TREE_CODE (e) == COMPLEX_EXPR)) return fold_convert_loc (loc, type, expr); if (TREE_CODE (TREE_TYPE (expr)) == ERROR_MARK) return error_mark_node; if (TREE_CODE (TREE_TYPE (expr)) == VOID_TYPE) { error ("void value not ignored as it ought to be"); return error_mark_node; } switch (code) { case VOID_TYPE: return fold_convert_loc (loc, type, e); case INTEGER_TYPE: case ENUMERAL_TYPE: if (sanitize_flags_p (SANITIZE_FLOAT_CAST) && current_function_decl != NULL_TREE && TREE_CODE (TREE_TYPE (expr)) == REAL_TYPE && COMPLETE_TYPE_P (type)) { expr = save_expr (expr); expr = c_fully_fold (expr, init_const, NULL); tree check = ubsan_instrument_float_cast (loc, type, expr); expr = fold_build1 (FIX_TRUNC_EXPR, type, expr); if (check == NULL_TREE) return expr; return fold_build2 (COMPOUND_EXPR, TREE_TYPE (expr), check, expr); } ret = convert_to_integer (type, e); goto maybe_fold; case BOOLEAN_TYPE: return fold_convert_loc (loc, type, c_objc_common_truthvalue_conversion (input_location, expr)); case POINTER_TYPE: /* The type nullptr_t may be converted to a pointer type. The result is a null pointer value. */ if (NULLPTR_TYPE_P (TREE_TYPE (e))) { /* To make sure that (void *)nullptr is not a null pointer constant, build_c_cast will create an additional NOP_EXPR around the result of this conversion. */ if (TREE_SIDE_EFFECTS (e)) ret = build2 (COMPOUND_EXPR, type, e, build_int_cst (type, 0)); else ret = build_int_cst (type, 0); goto maybe_fold; } gcc_fallthrough (); case REFERENCE_TYPE: ret = convert_to_pointer (type, e); goto maybe_fold; case REAL_TYPE: ret = convert_to_real (type, e); goto maybe_fold; case FIXED_POINT_TYPE: ret = convert_to_fixed (type, e); goto maybe_fold; case COMPLEX_TYPE: ret = convert_to_complex (type, e); goto maybe_fold; case VECTOR_TYPE: if (gnu_vector_type_p (type) || gnu_vector_type_p (TREE_TYPE (e)) /* Allow conversions between compatible non-GNU vector types when -flax-vector-conversions is passed. The whole purpose of the option is to bend the normal type rules and accept nonconforming code. */ || (flag_lax_vector_conversions && VECTOR_TYPE_P (TREE_TYPE (e)) && vector_types_convertible_p (type, TREE_TYPE (e), false))) { ret = convert_to_vector (type, e); goto maybe_fold; } break; case RECORD_TYPE: case UNION_TYPE: if (lang_hooks.types_compatible_p (type, TREE_TYPE (expr))) return e; break; default: break; maybe_fold: if (TREE_CODE (ret) != C_MAYBE_CONST_EXPR) ret = init_const ? fold_init (ret) : fold (ret); return ret; } /* If we are converting to nullptr_t, don't say "non-scalar type" because the nullptr_t type is a scalar type. Only nullptr_t shall be converted to nullptr_t. */ if (code == NULLPTR_TYPE) { error ("conversion from %qT to %qT", TREE_TYPE (e), type); inform (input_location, "only %qT can be converted to %qT", type, type); } else error ("conversion to non-scalar type requested"); return error_mark_node; } /* Create an expression whose value is that of EXPR, converted to type TYPE. The TREE_TYPE of the value is always TYPE. This function implements all reasonable conversions; callers should filter out those that are not permitted by the language being compiled. */ tree convert (tree type, tree expr) { return c_convert (type, expr, false); } /* Create an expression whose value is that of EXPR, converted to type TYPE, in a static initializer. The TREE_TYPE of the value is always TYPE. This function implements all reasonable conversions; callers should filter out those that are not permitted by the language being compiled. */ tree convert_init (tree type, tree expr) { return c_convert (type, expr, true); }